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We are experiencing an issue where an AF24 unit as Master is creating a loop when utilizing the same RX/TX frequency and no Slave unit is connected. Could we use RSTP to block the loop? If so, what settings are recommended?

I have been following your post over on the UBNT Forum
http://community.ubnt.com/t5/airFiber/A ... rue#M28116

I have come to the conclusion that airFIBER radios have no error correction between wireless interfaces.

Now let me explain why I have come to this conclusion.

I have a lot of AF24 links. We have fiddled with the cable to these links to make sure there are no cable errors and on bright sunny days with less than full wireless capacity these links produce no errors on the Ethernet interfaces.

Now as soon as rain rolls through and knocks the links down CRC's are recorded on the Switch Ethernet interfaces.

Also if you have 2 or more AF24 links interfering with each other CRCs appear on the Ethernet interfaces.

AF5X radios are more prone to CRC errors on the switch interface because they get more wireless interference and more corrupt packets obviously considering the noise on that spectrum verses 24 GHz.

Thus I have come to the conclusion that the radios are not making sure that packets get transferred from one radio to the other wireless wise error free before the packet is bridged to the Ethernet interface and passed to the switch or router.

I think this is because the CPU overhead that would be required to inspect and check every packet would be too much for the radio to handle with the given CPU power available plus the radio would have to deal with caching packets until they can be transmitted and received error free on the other side so they bridge all packets malformed or corrupted through and allow the Ethernet interface deal with the bad packets on the other side.

This also allows for lower latency when things are working as intended with no interference or signal fade.

So back to your problem, if the Tx and Rx are on the same channel then yes a packet that is transmitted could be received by the same radio and transmitted back at the interface it came from and would act as a loop.

However the only people that can answer this are the people at UBNT but I would guess that I am correct at least in principle if not completely correct as to how the AF radios handle wireless packet transmission, reception and then bridged to the Ethernet interface.

Great reply Chris. I agree with your assessment. Given this information, what is the best approach to utilizing AirFiber radios with your equipment?

Another thing that I have noticed with a AF5x link plugged into a Netonix switch - when a production link drops, it seems to create a loop and kill all traffic (same as AF24). However, there doesn't appear to be a way to truly change the RX/TX frequencies. I have experimented with utilizing TDD with no success. Do you have any experience or advice with this?

Any advice regarding AF24 should I choose to utilize the same RX/TX frequencies?

zrob_12 wrote:Any advice regarding AF24 should I choose to utilize the same RX/TX frequencies?

My advice is do not use the same RX/TX frequencies.

I have never seen loops with my AF radios, I am speculating on a "possible" cause when using the same RX/TX frequencies on AF24.

I am not even sure that is what is happening?

I am just suspect that AF radios pass wireless packets regardless if they get corrupted in transmission.

Thoughts on AF5x?

I'm assuming RSTP will not help?

zrob_12 wrote:I'm assuming RSTP will not help?

Loop Protection would be better for this then RSTP but it will shut the port down for 90 seconds

Thank you!